A robot joint is an important component of a robot system, which directly affects overall performance of the robot system. In recent years, with rapid development of service robot, relationship between robot and human becomes increasingly closer, and whether a robot system can have a good interactivity with human and environment becomes the focus of attention.
In conventional robot design, the design method of a joint mainly adopts a rigid-type design, where motors, reducers etc. are used as driving units of a robot joint. Such design of a robot joint lacks a flexible unit, resulting in that the robot joint is easily damaged by an external impact, thus directly affecting normal operation of the robot. In recent years, designers have turned their attention to methods of designing flexible joints and provided methods of designing a flexible joint having a force/torque transducer and serial elastic driving joint etc., so that the effect of the external impact on the operating joint in a robot can be avoided, thus creating a good condition for interaction between the robot, human and environment. However, anti-external impact performance of a flexible joint based on a force/torque transducer leaves much to be desired because the joint itself does not possess flexibility, the joint based on serial elastic driving possesses fine anti-impact and force sensing performance, but most of the joints adopt conventional spiral springs, and it is difficult to design a smaller, lighter joint with a compact structure. WANG Liquan et al. of Harbin Engineering University developed an elastic driving rotary joint disclosed in Chinese patent No. CN 102152319A and a double-serial elastic actuator disclosed in Chinese patent No. CN 101318331, both of which adopt the conventional spiral spring. Planar torsion spring for a robot joint has not been developed in China.